Field of the Invention
The aspect of the embodiments relates to signal processing for performing video display at an absolute luminance of an object.
Description of the Related Art
Conventionally, the dynamic range of an output of a display apparatus, such as a television or a display, is considerably small compared with an actual object, and a video of the object can be displayed only in a limited dynamic range. To that end, in imaging an object with an imaging apparatus, it is necessary to compress the dynamic range so as to squeeze a video signal with a wide dynamic range into the dynamic range corresponding to the output of the display apparatus. Such processing causes the display apparatus to display a video with a state different from an actual appearance, and realism is lost.
For example, assume that the dynamic range of a video signal is compressed in such a manner that a face to become a main object has brightness of about 70% of an output of a display apparatus. In such a case, the face is displayed with brightness appropriate for viewing. However, since the brightness of the video is different from actual brightness, the realism is lost. Moreover, the tone of an object brighter than the face is largely compressed and lost in the video.
In recent years, performance of display apparatuses has improved, which has made it possible to express a wider dynamic range.
However, in a case where a display apparatus capable of expressing a wide dynamic range displays a video captured by a conventional imaging apparatus, the captured video is displayed with unsuitable brightness with respect to an actual object in some cases. Thus, it is necessary to perform processing different from video-signal processing performed in the conventional imaging apparatus.
For example, assume that processing is performed so that a face to become a main object is about 70% of an output of a display apparatus. In this case, if the display apparatus can support 10000 cd/m2 at the maximum, the face is displayed with brightness of 7000 cd/m2, which is unrealistic brightness.
As discussed in Japanese Patent Laid-Open No. 2004-286979, tones to be reproduced can be addressed by performing suitable tone processing according to an absolute luminance of an object. However, this is not enough to enable a display apparatus to display the object with the same brightness as that of the object when actually viewed.